Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Natural convection


Variation of Heat Transfer Coefficient for Inside and Outside Closed Space with Respect to Temperature Gradient for Three Different Metals

M.M. Hamadi; Z.H. Mohsein

Engineering and Technology Journal, 2017, Volume 35, Issue 5, Pages 537-545

The heat transfer coefficient (h), is used in thermodynamics to calculate the heat transfer typically occurring by convection. A simple way to calculate (h) is to define it through the classical formula for convection, the present study includes correlations different natural convection can be used to calculate heat transfer coefficients theoretically for the experimental tests done inside and outside close system. All the results obtained from the experimental tests, theoretical calculations and from the literatures show that, heat transfer coefficients (h) are increasedwiththe temperature increasing. The experimental results for all the tested materials appears that there are similarity for the rules of sequence step in the change of heat transfer coefficient (h) with respect to the thermal conductivity coefficients (k) of these materials, and they are in a row from the highest value to the lowest value; Copper, Aluminum, Steel and Brick respectively for both of (k) and (h). The results show a good accuracy and compatibility of the comparison between numerical results with the present experimental work, also give a good agreement between the present experimental work and the numerical results with the experimental results obtained from literature approved in this study.

Numerical Study for Natural Convection within a Rotating Cubic Enclosure

Hussein Majeed Salih

Engineering and Technology Journal, 2012, Volume 30, Issue 16, Pages 2792-2810

A numerical study of three–dimensional, steady, turbulent and incompressible
natural convection of air (Pr=0.72) within a rotating cubic enclosure is presented. The
present code is based on solving partial differential equations for conservation of
mass, momentum and energy equations for a rotating frame. The turbulence effect is
introduced by using two equations turbulence model of k-e . Finite volume method is
used in solving the governing equations. SIMPLE algorithm is applied to solve the set
discretization equations. To verify the validity of present method, present results is
compared with those of previous published work under the same conditions. The
influence of changing rotation Rayleigh number (Rar ) as a result of chancing
angular velocity of enclosure, and temperature difference of enclosure walls on the
average Nusselt number (Nu) is presented and correlated.

Numerical Study of a Solar Chimney Power Plant

Rafah A. Najim; Jalal M. Jalil

Engineering and Technology Journal, 2012, Volume 30, Issue 15, Pages 2597-2608

Axi-symmetric, steady, incompressible, turbulent flow field developed by natural convection inside power plant solar chimney is investigated numerically using finite volume method. Navier-Stockes with energy equation is solved to achieve velocity components and temperature distribution inside solar chimney. To complete the thermal analysis, conduction through upper glass wall, chimney concrete wall and floor ground were investigated to calculate temperature distribution through theses walls. A standard turbulence model associated with lawss of the wall along solid boundaries was used. Special arrangement for mesh was used to deal with complicated shape of the domain. The main studied parameters are solar collector diameter, kinds of ground, periphery heights and solar intensity radiation. This study was compared with previous available experimental study and there is acceptable agreement. The performance of the solar chimney was examined through maximum air velocity in the tower inlet and maximum temperature in the ground floor. The final optimization parameters are defined within studied ranges.

Numerical Simulation for Laminar Natural Convection with in a Vertical Heated Channel

Hussein Majeed Salih

Engineering and Technology Journal, 2011, Volume 29, Issue 11, Pages 2298-2311

A numerical investigation has been performed to estimate the induced flow rate for a laminar natural convection flow of air in a vertical channel with isothermal walls conditions (one hot and another is cold). The two-dimensional governing equations have been solved using finite volume method. The coupling between the continuity and momentum equations is solved by using the SIMPLE algorithm. After the validity of the present code by comparing results with these of previous study for the similar conditions, solutions have been obtained for Prandtl number of 0.7, aspect ratio of (4 to 20) and wall temperature difference of (10 to 30). The effects of the changes in these parameters on the induced flow rate, Grashof number and flow
patterns within the channel have been predicted. A mathematical form of flow rate correlation is presented for these cases.

Numerical Study Of Turbulent Natural Convection In An Enclosure With Localized Heating From Left Side

Ali L. Ekaid

Engineering and Technology Journal, 2009, Volume 27, Issue 14, Pages 2692-2710

In this work, a numerical study is performed to predict the solution of buoyancy turbulent flow and heat transfer inside a square cavity with localized heating from the left side wall. Full Navier Stockes and energy equations were solved using Finite volume method with a non-uniform staggered grid. The studied Rayleigh numbers were
ranged between 1E108 to 1E1012 and Pr=0.72. For the purpose of the analysis, the heated dimensionless length L/H is varied from 0.2 to 0.8. The k-ε model with standard wall function is used to treat the turbulence in the flow. The obtained results show that the strength of the induced recirculating velocity is increased with the increase of Ra. Also the results displaced that the average Nu is increased with the increase of Ra. However the average Nu number is decreased with increasing of dimensionless heated length